This disclosure relates generally to magnetoelectronics, and more specifically, to a method for patterning magnetic tunnel junctions (MTJ).
MTJ patterning or etching processes are used to fabricate MTJs. Currently known methods for MTJ etching include ion beam etching (IBE) and chemical etching in a reactive ion etching (RIE). RIE process tends to cause sidewall damage on MTJ due to oxygen or corrosive chemicals and results in the degraded magnetic tunnel junction properties. An IBE process can avoid or reduce damage zones over RIE processes, but no chemical component is involved to improve etching selectivity. IBE involves directing a charged particle ion beam at a target material to etch the material. IBE is typically performed with a 30 to 50 degree angle with respect to the wafer surface with a fast and uniform rotation of the wafer. As MTJs become scaled down with tight pitch, such as in high-density MRAMs, IBE with uniform wafer rotation results in the shadowing of ion beam etching between pillars increase. It becomes very difficult to achieve vertical sidewall angle and remove the footings between pillars which result in the shorting between MTJ pillars. There is a growing demand to enhance etching efficiency of tight pitch pillars for technology extendibility.